The present invention relates to a tilt holding force adjusting mechanism for a steering column, and more specifically to a tilt holding force adjusting mechanism enabling fine adjustment of a tightening force in a tightening operation of a tilt lever on a tilt bolt.
In a tilt steering column, a distance bracket is fixed and released in an upper clamp by applying or removing a tightening force of a tilt bolt tightening the upper clamp with a rotatable tilt lever. In the released state, the distance bracket is movable up and down, and the steering column supported by the distance bracket is adjustable at a desired inclined angle.
As shown in FIG. 7, a jacket tube 2 receives a rotatable steering shaft 1 coaxially. The jacket tube 2 is fixedly mounted on the distance bracket 3. The distance bracket 3 is movable up and down in the upper clamp 4 fixed to a vehicle body. A tilt bolt 6 passes through vertically elongated apertures 5 formed in right and left side walls of the upper clamp 4 and holes of the distance bracket 3. A first end portion of the tilt bolt 6 engages a tilt lever 7 and a second end portion of the tilt bolt 6 engages a tilt bolt stopper 8 serving as a rotation preventing detent member. These members constitute a tilt holding force adjusting mechanism. The upper clamp 4 can fasten or release the distance bracket 3 when the tilt lever 7 is rotated in a forward or reverse direction.
As shown in FIG. 8, the first end of the tilt bolt 6 has a threaded portion 9. A nut 10 is fixed to the tilt lever 7, and screwed on the threaded portion 9. The second end portion of the tilt bolt 6 is integrally formed with an outward flange 11. Serrations 12 are formed on the outside periphery of the flange 11. The tilt bolt stopper 8 has a hole and first and second projections 14. Serrations 13 are formed on the inside circumferential surface of the hole of the tilt bolt stopper 8. The hole of the stopper 8 receives the flange 11, and the external serrations 12 of the flange 11 engage with the internal serrations 13 of the hole. The projections 14 of the tilt bolt stopper 8 are integrally formed in the stopper 8 at diametrically opposite positions across the hole. The projections 14 engage in one of the elongated apertures 5 of the upper clamp 4 and thereby prevent rotation. When the tilt lever 7 is operated rotationally, the tilt bolt 6 is prevented from rotation. A push nut 15 holds the tilt bolt stopper 8 on the second end of the tilt bolt 6 by pressing the tilt bolt stopper 8 to the side wall of the upper clamp 4 in order to prevent falling.
The threaded portion 9 of the tilt bolt 6 is in the form of left hand screw in order that the upper clamp 4 fixes the distance bracket 3 when the tilt lever 7 is operated in the direction of lifting.
In the conventional tilt holding force adjusting mechanism of the tilt bolt 6 and the tilt bolt stopper 8, however, the adjustment of the clamping force of the upper clamp 4 clamping the distance bracket 3 requires the disengagement and reengagement of the serrations 12 and 13. The adjustment of the clamping force minutely requires a complicated and time-consuming operation to adjust tooth by tooth by dismantling and reassembling the adjusting mechanism.